Re: SCPC Detection Program

[Noah Lavine]

Michael,

I see your point about version numbers, but I don't think it's as good
to add a hint to the Tramp manual, because users still have to look
through it to see that it's there and then configure Tramp. In
general, I think it's safe to assume that they will read the manual as
little as possible in order to accomplish whatever task they're trying
to accomplish.

For instance, I used Tramp for a while before I realized that there
was a way to make it stop asking for my password all the time. This is
basically my effort to make sure that this doesn't happen to other
users in the future.

Is there a commonly-used way to discover the capabilities of a system
other than version numbers? Talking to the system package manager
would also work for most (although not all) cases, and I could look
into writing a connection to PackageKit if that seemed like it could
work.

It would also be really cool if the ssh program had a way to tell us
what command-line arguments it accepted, but I don't see any way to do
that short of asking it to open up a test connection and seeing if it
gave an error message. That might actually be a reasonable way to do
this, if you defer the checking until the first use of ssh - first try
opening a connection with ControlMaster, and if that fails, try again
without it.

Noah

On Sun, Apr 11, 2010 at 12:19 PM, Michael Albinus
<address@hidden> wrote:
> Noah Lavine <address@hidden> writes:
>
>> Dear Tramp Developers,
>
> Hi,
>
>> I recently started using Tramp and learned about the different access
>> methods. As I understand it, the `scpc` method is superior to the
>> `ssh` method, but can't be set as default because of old versions of
>> ssh that don't support the ControlMaster argument.
>>
>> It seems to me that it would be better if Tramp could automatically
>> detect whether the version of ssh on a computer supported the
>> ControlMaster argument and use scpc if it were possible. Therefore, I
>> started working on a program to detect this based on the SSH version
>> string. The following program correctly detects the presence of an SSH
>> version greater than 4.0 on my computer:
>
> I am not too happy in detecting features by checking version numbers of
> programs. This will work for a while, and this will generate problems
> later on, likely.
>
> Maybe it is sufficient to add a hint to the Tramp manual, that the
> following setting in the ssh config file is useful, when applicable by
> the underlying ssh version:
>
> Host *
>        ControlMaster auto
>        ControlPath   /tmp/address@hidden:%p
>
>> Noah Lavine
>
> Best regards, Michael.
>